Bartonella is a genus of Gram-negative, facultative intracellular bacteria. Bartonella species are responsible for a range of diseases in animals and in humans. Some species have been recognized as emerging pathogens. The wide range of disease manifestations caused by Bartonella depends on the infecting species and the immune status of the patient. Most Bartonella species are sensitive to quinolones in vitro, though treatment failures have been reported. Quinolones vary in their antibacterial spectrum and activity. Fluoroquinolones, a type of quinolone, effectively inhibit DNA synthesis by disrupting DNA breakage-reunion reactions. Ciprofloxacin is a fluoroquinolone that inhibits the bacterial enzymes DNA gyrase and topoisomerase IV.